i9o6] DE VRIES— ELEMENTARY SPECIES IN AGRICULTURE. . 155 



It remains to be shown that the new facts give sufficient proof 

 of the exactness of this suggestion. They relate to the question of 

 the part which fluctuating variabihty and mutabiUty may have 

 played in the selection culture of Rimpau. An exact notion of the 

 first phenomenon, as stated by the works of Quetelet (1870) and 

 Gal ton (1889) had only found its way into botanical investigations 

 about the year 1894, or nearly twenty-five years after Rimpau started 

 his pedigree of rye. At his time, therefore, no distinction of this 

 kind could be made, and it is only natural that he took his selected 

 specimens to be the extremes of ordinary fluctuating variability 



This point of view and this lack of distinction between the now 

 so clearly contrasting processes has prevailed for a long time among 

 agriculturists. As an instance I may quote the work of Willet M. 

 Hays, now in Washington (1899, Bull. No. 62, Agric. Exp. Station, 

 Minnesota) . He has ameliorated the wheat of Minnesota by breed- 

 ing, from the local races Fife and Blue Stem, better and more yield- 

 ing varieties, which now in large part have supplanted the old types. 

 Besides his practical results he has given some theoretical considera- 

 tions in which he compares his selected mother plants with the prin- 

 ciple of fluctuating variability and explains them as extremes in the 

 curves which constitute the law of Quetelet. '' In each one thousand 

 plants of wheat," he says, '' there are a few phenomenal yielders, and 

 the method of single-seed planting makes it practicable to secure 

 these exceptional plants, and from these new varieties can be made " 

 (p. 429). But according to our present knowledge, the isolation of 

 such plants, if they were truly extremes of fluctuating variability, 

 would lead to a regression to mediocrity, as it has been called by 

 Galton, and not to constancy nor to an exact keeping up of the 

 extreme type. Therefore the supposition is allowed that the phe- 

 nomenal yielders of Hays, were in reality representatives of distinct 

 elementary species, which had been hidden until his time. His 

 method of selecting enabled him to single them out, and his new 

 principle of single-seed planting, which conduced to his high achieve- 

 ments, at the same time indicated the way for an explication on 

 the basis of our present views concerning the different types of 

 variability. 



